Kawizx9r

iTrader: (2)

Ok so I introduced myself 3+weeks ago and afterward acquired a 1993 FD automatic.

It's 99% stock aside from;
Greddy Profec EBC, after-market downpipe (to eliminate pre-cat), aluminum radiator, samco radiator hoses, tokico whites.

I picked up my FD because I've always wanted a rotary but didn't want to drop 15k+ on those that were on ebay/craigslist locally so the one I have ended up being an automatic. I'm hoping that'll change seeing as how I have a 5-speed rebuilt transmission from another FD in the garage, just need all other required parts.

Anyway, I ask here because after 3-4 days of searching as well as checking out the car and driving it to test theories out I can't figure it out for the life of me (before replacing parts).

Upon accelerating (non-wide open throttle) if I feather the gas and stay at about 1/4 throttle, the car sputters and the rpms drop and stay at about 1.2k rpm.

It's when I'm in the city, I try to drive the speed limit and well to eliminate this problem I have to gain room from the car ahead of me and press the throttle a little more than 1/4 in order to move forward without sputtering. This of course builds up boost and moves the car quickly. I'm not new to turbo cars (I've owned 4 others) and after driving alot, the car;

-comes to a sputter, even if I'm at 2.9k rpm if I'm at 1/4 throttle and drops down to the 1.2-1.5

-does not sound like it's misfiring at all, boost comes on quickly if I go slightly more than 1/4 throttle

-sputters even if I'm in L gear or S as I'm driving, even at higher speeds like at 40mph

At first I thought it was the spark plugs, and I'll change those regardless upon next oil change. Next thought is the throttle position sensor, but could it be that if it happens ONLY at a certain position of the throttle? I have also looked in and out from above and below the car and all vacuum lines are intact still...and yes I will replace those soon. I was also thinking about cleaning the throttle body but I can't imagine why it would consistently create the sputtering effect at only 1/4 throttle.

Any ideas or is this common before I go purchasing parts and start taking things apart? I feel like I belong here cause this forum does their own work on their cars like myself

Kawizx9r

iTrader: (2)

Bump.

If you didn't read the above, that's fine. I could just start a new thread but anyone can feel free to read the above.

Recently, my MAP sensor became disconnected. Zip-tied stuff up and all was well again...in fact even the sputtering was gone that occurred ONLY when I was 1/4th throttle (as described above, the point of this thread).

Now, each day since then the sputtering@1/4th throttle ONLY HAPPENS AT NIGHT!

I was thinking maybe because it's cold outside? However, this morning@7am there was no sputtering at all (and yes it was cold outside). However, tonight it happened again...same as last night and the night before.

I thought to myself well maybe it's because I use the car throughout the day? I used it once today, it sat there all day until night time. I let it warm up for like 10 minutes, go drive and sputtering@1/4th throttle.

It happens at night, it doesn't happen on cold mornings but it does at night whether it's a bit colder/warmer than it was in the morning. What gives?

I would've come to a solution already by checking/calibrating my TPS sensor. I found the write-up (one of them) and guess what? I have philips head screws holding my TPS sensor....NOT 7mm bolts as suggested on two different pages/sites.

Still narrowed down to TPS or MAP sensor? Keep in mind, I check the MAP sensor lines all the time and it's been very secure since using zip-ties.

I ask cause I have limited time and can't be busy trouble shooting/replacing stuff. Barely have enough time to calibrate the TPS if I had a tool/philips head at hand to get in there and undo the screws.

Banzai-Racing

iTrader: (11)

You may have a voltage issue, dieing alternator or battery. You say the problem happens at night, do you have the lights on?

I do not know why you have Greddy EBC on such a stock car, what boost are you running?

The auto FD can be a great car, we developed the adapter to install the Power FC, this allows the car to be tuned and modified safely. It also allows you to view all of your sensors and switches on one screen, this means you could view your TPS voltage in a second and see if it needs calibration.

He's On Toroids

iTrader: (2)

Check ALL of your grounds and make sure they are clean/getting good contact. Your electronics could be fine but getting screwed up by bad grounding. And I mean all of them, even your grounding straps to your exhaust.

Also, how old is your O2 sensor? I don't know if it was exactly the same symptoms as you are having but when mine went bad the car would sputter like you describe whenever I was low throttle (when the stock ECU uses the O2 feedback). It happened sporadically for a while and was hard to diagnose since I didn't get any engine codes. Eventually when it started to fully fail I got a code, but it didn't stay on the dash. I'd check your ecu codes just to make sure it didn't save one while you weren't looking.

DaleClark

iTrader: (55)

Get some new plugs in there ASAP. Bad plugs will do all kinds of weird stuff, and that's step #1 when troubleshooting problems like this.

Dale

Kawizx9r

iTrader: (2)

Battery is months old, so maybe I'll get them checked out free at the local autozone.

As for the EBC, it's not HOOKED up...just there. Previous owner had on there but boost levels are left alone. This isn't my first turbo car, just my first rotary.

I recall reading about the grounds prior to purchasing my FD. Other than the common one such as battery/etc. are there any specific grounds I should be wary of that could have a bad connection?

As for the o2 sensor, it's only 2-3 months old. I've had a bad o2 sensor before and it's not that kind of sputtering...but thanks for the suggestion!

Will do then. I would've purchased them already but you can't imagine how many different threads/posts I've read when the question 'what plugs do I use' was asked. I haven't picked any up because some said 'this kind' for trailing and this kind for 'leading' and then another individual said no, you got them backwards etc. Hard to find out which one's right and which one's not

He's On Toroids

iTrader: (2)

Here is a photo that highlights the grounding locations of an FD. I'd check them all.

Credit to Damian

RotaryEvolution

iTrader: (30)

i can't emphasize it enough but start with regular maintenance items first before moving on to troubleshooting.

inspect/replace the:

spark plugs
fuel filter
plug wires(if they are unknown age)
vacuum lines if they are original(inspect for broken hoses)
clean the fuel pump sock
do a compression test

from there if the problem still exists at all you can move on to checking other things like voltage to the fuel pump, fuel pump pressure, check AFRs with a wideband to see if it is a fuel system issue or something else...

Banzai-Racing

iTrader: (11)

Your car is stock, so put in stock (7 & 9) NGK plugs & wires

http://www.banzai-racing.com/store/9..._ignition.html

Kawizx9r

iTrader: (2)

Thanks so much!

I was planning on checking the ECU wiring as well in the passenger side floor/quarter panel area.

In just the past year, I've had about 11 different cars and trust me I do this with ALL cars before doing ANY modifications/work.

Car has already had an oil change, and the previous owner (I asked for receipts) had replaced the spark plugs 600ish miles ago (well, 200 but I put 400 on the car). Wires are plugged in and look to be in good shape but I'll replace those anyway when I do the spark plugs.

Vacuum lines are of the same OEM type, most were replaced when the motor was pulled and rebuilt...but like I said unfortunately the same type were used instead of after-market lines. Full kit is only like 110 bucks, don't see why no one would do it so I'll have to take on that task in the near future.


Gotcha, like I said I did a search and it pulled up NGK (forget the part number) but even on the same thread people kept mixing up plug types for the leading and trailing.

And an update btw, I'm narrowing this all down to a ground issue.

After posting earlier, I went to school and no sputtering. Turn on my headlights, sputtering. So either alternator, battery (which I doubt but doesn't hurt to check), and grounds.

Thanks guys, definitely saving that picture for future reference lol

RotaryEvolution

iTrader: (30)

you forgot to mention the fuel filter, of which i bet is original still. it's sad how neglected they get on the FDs due to the pain in the *** where they are located.

Kawizx9r

iTrader: (2)

I bet it is too, and hoping it'll get taken care of when I get new motor mount bolts on my other car so I can have downtime on the RX-7.

Kawizx9r

iTrader: (2)

As shown in the picture, I was unable to check 5 grounds;

1. UIM to frame ground (under air filters)...THIS GROUND IS MISSING!
2. Battery ground and Engine Block A,
3. Engine block ground A
4. Engine block ground B
5. Under the car grounds

Was too busy, but I did get a chance to clean/sand the one on the UIM to body and UIM to engine block ground B.

My question is, would a missing ground (simply a missing wire, so less of a ground) possibly cause the sputtering when headlights are on? I'll get to checking the other grounds tomorrow since I have no school...but I ask because I'm missing the ground that goes from the UIM to the frame ground under the air filter box.

I know how/why grounding works, and wondering if I should just run a 4 or 8 gauge wire from the UIM bolt (where the other ground stems from) and just run it to the frame under the filter? I mean, in that case..I don't have to run it to that specific location if I'm just adding another ground wire right?

I also found what I think is my...sender/pressure unit(?) that's under the oil filter, it had a cut wire, thinking that's why my oil pressure gauge doesn't work (although I heard they're crappy anyway and fail). Not only that, I found a loose harness under the car...a tiny plug and couldn't find where to plug it in.

Really wish I had a service manual, I wouldn't ask so damn much on here lol I'll take a pic of the wire later, if I don't follow it's location and find out what the hell it is beforehand.

ttmott

iTrader: (1)

This may be the infamous chronic 3000 RPM hesitation that is indicative of the Mazda ECM. For some reason and I don’t think anyone has really isolated the issue the car will feel like it is stalling at steady state throttle and start bucking at throttle tip-in. The issue is really apparent around 3000 RPM. With the automatic trans. the magnitude of the issue may be dampened.
I would pull the ECM codes to see if anything pops out. The CEL doesn’t light up for everything.
Regardless, get everything on the car checked and updated (grounds, filters, plugs, etc) then move from there. Also change the plug wires.
After the updates clear any ECM codes then drive and pull any codes if any and react from there.
The only way I was able to get rid of the hesitation / buck issue was to move to the PFC ECM.

The Factory Service Manual, Wiring Diagram and Body Electrical Troubleshooting Manual are all available on this site - Look through the stickies.

Banzai-Racing

iTrader: (11)

The picture posted is not of the factory grounding locations. That is if you want to add grounds.

The FSM is available online for free.

He's On Toroids

iTrader: (2)

Yeah sorry I didn't explain fully. That picture is of Damian's setup using the hyper-ground system. It does show the factory ground locations but also some additional ones added using that system. I would add them if you are inclined since you can't over do it on grounds

I wouldn't be too worried about the empty harness that you found. I've found a few on my car either from accessories that are no longer there, or options that my car doesn't have. I'd still track down what it is so you can make sure, but don't loose any sleep over it

Kawizx9r

iTrader: (2)

I'll find out how to pull engine codes when I can and I'll do so and see if anything comes up.

As for the '3k rpm hesitation', I've read about this briefly but as I stated above...it's at below and/or after 3k rpm.

For instance; I'm driving my car on the road and the speed limit is 40mph. I'll have my pedal at 1/4th throttle, which puts me at about 2.1k rpm@40mph. Now, I'll turn on the headlights...within a minute or less, the bucking/sputtering occurs at that 2.1k rpm and the rpms will continue to lower until about 1k rpm. Keep in mind, I didn't let off the throttle at all...it's as if I wasn't giving the car any gas. If I press a bit further than 1/4th, suddenly it lurches forward and registers that 'more than 1/4th throttle'. This happens at 65+mph at different rpms, even going from a stop from 0-10mph it sputters if my lights are on so rpm's are inconsistent.

Gotcha, thanks. I've checked out other stickies and didn't run into it. Since it's online for sure, I'll take a look again.

No worries.

I did read about someone else finding a loose connection, and it happened to be for his cruise control...or lack thereof. Makes sense that the factory ran the harness/wiring but didn't have said-component if the car didn't come with it equipped from the factory. It's just in a weird location...trailing down from the side of the engine (driver side) and comes straight down to underneath the car. I found it when I tightened the hose to the hardline coming from the oil cooler.

ttmott

iTrader: (1)

[QUOTE=Kawizx9r;10832499]I'll find out how to pull engine codes when I can and I'll do so and see if anything comes up.

As for the '3k rpm hesitation', I've read about this briefly but as I stated above...it's at below and/or after 3k rpm.

For instance; I'm driving my car on the road and the speed limit is 40mph. I'll have my pedal at 1/4th throttle, which puts me at about 2.1k rpm@40mph. Now, I'll turn on the headlights...within a minute or less, the bucking/sputtering occurs at that 2.1k rpm and the rpms will continue to lower until about 1k rpm. Keep in mind, I didn't let off the throttle at all...it's as if I wasn't giving the car any gas. If I press a bit further than 1/4th, suddenly it lurches forward and registers that 'more than 1/4th throttle'. This happens at 65+mph at different rpms, even going from a stop from 0-10mph it sputters if my lights are on so rpm's are inconsistent. QUOTE]

Yup - that seems to be consistent with what I experienced and falls in the 3K hesitation topic. I did all of the ground modifications thinking that the extra electrical load (like truning lights on) was taxing a marginal ground system but didn't fix. You might take a look at the EL module. This little device detects demand from the alternator and increases RPM to compensate for a drop in engine RPM's from the alternator's drag. It has an input to the ECM and changes the timing and/or IAC valve. Long shot but as I said I had enough and changed the ECM. You can get one of these Electrical Load Modules cheap in the used parts section.

He's On Toroids

iTrader: (2)

So right around those two soft L shaped hoses that connect the hard-lines from the cooler to the hard-lines on the trans? That is where most of the electrical connections to the transmission are made (Park/neutral switch, vehicle speed, etc). Also the starter harness isn't to far from their either. If you can tell me how many pins the connector was and what color the wires were I'll probably be able to tell you what it is for.


Oh, and checking engine/trans codes are easy here are the cliffs notes:

1: find paperclip
2: bend it into a U
3: open hood & prop it up
4: find Diagnostic port and flip up cover (it is a little 1"x1" box back about 6" from the battery and over closer to the fender says Diagnostics right on the top of it)
5: under the lid of the diagnostic box is a picture that has each pin of the connector labeled. Stick the ends of the paperclip into the pins corresponding to TEN and GND.
6: get into drivers seat and turn key to accessory.
7: count and write down blinks of the CEL (tens digit are 1.2s long, ones digit is 0.4s). when you see the start to repeat, turn key off and remove paperclip.
8: done

To pull trans codes it is the same thing only you jumper TAT and GND then look at the HOLD light flash instead of the CEL.

For full story see: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/how-read-fd-trouble-codes-851414/